The present invention relates to a system for rapidly changing die shoes in a press, and in particular for rapidly changing die shoes having at least one fastener installation head that is used in installing fasteners in the part being formed.
A conventional press generally has a first die shoe clamped to a ram which is reciprocated with respect to a second die shoe clamped to a base. A blank of material is passed between the die shoes and is stamped into the desired shape by the reciprocating ram. The stamped part is then transferred out of the press and another blank of material is received. Instead of single blanks, a roll of material may be used and continually fed into the press with each successive stamped part being cut from the roll by the press.
In a later station in the press or simultaneously as the part is being formed, one or more fasteners may be pressed into the part. One example of such a fastener is a self-piercing nut as disclosed in U.S. Pat. No. 3,648,747, assigned to the assignee of the instant application and incorporated herein by reference. The self-piercing nut includes a pilot portion which pierces an opening in a panel, a pair of flanges on opposed sides of the pilot having panel-bearing faces and re-entrant grooves in the flange-bearing surfaces adjacent the pilot. Upon forced engagement with the panel, the pilot pierces an opening in the panel and the pierced panel edges are deformed into and retained by the re-entrant grooves.
Preferably, the self-piercing nut is installed by an installation head mounted in one of the die shoes. An example of such an installation head is disclosed in U.S. Pat. No. 4,505,416, which is also assigned to the assignee of the instant invention and incorporated herein by reference. The installation head generally has a stationary member for attachment to a die shoe and a relatively moveable member. The moveable member includes a first passage for receiving the pierce nut and a transverse plunger passage intersecting the first passage. A plunger is connected to the stationary member and projects into the plunger passage of the moveable member in telescopic relation.
Briefly, self-attaching fasteners or pierce nuts are received in the movable member beneath the plunger. When the moveable member engages a panel supported on a pierce or clinch die, the moveable member is moved toward the stationary member, telescoping the plunger in the plunger passages and installing the fastener in the panel.
The installation head is continually supplied fasteners through a chute which is interconnected between the installation head and a supply of fasteners with each installation head requiring a separate chute. The chutes must be threaded through the ram or base and the adjoining die shoe for connection to each installation head. Further, in some applications, power must be supplied to the installation head and related control means, such as control valves.
To remove the die shoe containing the installation heads, each chute and power line must be disconnected and pulled out of the die shoe. With several heads, a die change can be extremely time consuming. Since the press is inoperative during this period, considerable production time is lost.